BAGHDAD (Reuters) - Iraqi forces clashed with Islamic State militants near Falluja on Monday while bombing central districts in the initial hours of an offensive to retake the militant stronghold just west of Baghdad that could take several weeks.
Some of the first direct engagement occurred in al-Hayakil area on the city's southern outskirts, a resident said. Air strikes and mortars overnight targeted neighborhoods inside the city proper where Islamic State is thought to maintain its headquarters. But the bombardment had eased by daylight.
Residents living in the center said they had fled to relative safety in outlying northern areas but roadside bombs planted by Islamic State prevented them from leaving the city.
Falluja, a longtime bastion of Sunni Muslim jihadists, 50 km (30 miles) from Baghdad, was the first city to fall to Islamic State, in January 2014. Six months later, the group declared a caliphate spanning large parts of Iraq and neighboring Syria.
Iraqi forces have surrounded the city since last year but focused most combat operations on IS-held territories further west and north. The authorities have pledged to retake Mosul this year in keeping with a U.S. plan to dislodge Islamic State from their de facto capitals in Iraq and Syria.
But the Falluja operation, which is not considered a military prerequisite for advancing on Mosul, could push back that timeline. Two offensives by U.S. forces against al Qaeda insurgents in Falluja in 2004, which left the city badly damaged, each lasted about a month.
Prime Minister Haider al-Abadi, who also faces political and economic crises in the major OPEC producer, visited a command center set up nearby to oversee operations, state television said on Monday.
Abadi, announcing the offensive in a late-night speech, said it would be conducted by the army, police, counter-terrorism forces, local tribal fighters and a coalition of mostly Shi'ite Muslim officials.
Iraqi officials say the militias, including ones backed by Iran, may be restricted to operating outside the city limits, as they were largely in the battle for nearby Ramadi six months ago, to avoid aggravating sectarian tensions with Sunni residents.
State television showed footage of armored vehicles sitting among palm groves on the city's outskirts, a green tracer glow emanating from shells and machine gun fire.
Video showed a family standing in the daylight outside a simple one-storey home, cheering and waving a white flag as a military convoy passed by.
Iraqi and U.S. officials estimate there are as many as 100,000 civilians still living in Falluja, a city on the Euphrates river whose population was three times that size before the war. Besieging the city has created acute shortages of food and medicine.
The government has called on civilians to flee and said it would open safe corridors to areas south of the city, but bombs planted by Islamic State along the roads are complicating evacuation.
(Reporting by Ahmed Rasheed; Writing by Stephen Kalin; Editing by Richard Balmforth)